This invention relates generally to actuators, and, more particularly to an actuator which by the application or removal of fluid from a plurality of pressure tubes is capable of providing a continuous force.
In general, actuators are designed in the form of piston and cylinder arrangements. There are many instances where such an actuation system is unacceptable, either because the motive force provided is insufficient, actuation is unreliable, and/or the overall cost of the actuator fails to fall within the cost limitations of the system in which the actuator is used.
Some systems in which currently available actuators may be less than desirable would be, for example, in driving the forming head of a sheet metal brake forming machine, driving the clamping jaws on a two-way or four-way stretch forming machine, applying appropriate force to the segmented brake shoes on wheel brakes and varying the chord or diagonal member dimensions in a variable geometry truss as applied to a variable camber leading or trailing edge device.
The latter application is of particular interest since the variable camber concept offers significant improvement in the overall aerodynamic efficiency of aircraft such as the FB-111 that operate in a variety of different mission segments. The efficiency improvement of such aircraft is obtainable by means altering the chordwise and spanwise geometry of the wings to provide optimum aerodynamic characteristics during takeoff, climb out, subsonic cruise, in-flight refueling, subsonic sea level or high altitude dash, supersonic cruise and landing.
Actuators which have been considered for varying the wing geometry generally include conventional hydraulic actuators, power hinges or screw jacks which could be utilized with cables, pulleys and actuating linkages in order to produce such movement. Unfortunately, as the operating speeds of aircraft increase, conventional actuating means have proven to be unsatisfactory and inadequate in obtaining sufficient alteration of the wing or airfoil design. Consequently, there arises a need for not only an improved actuator which is capable of providing continuous force but also an actuator which is readily adaptable for use in varying the chord or diagonal dimensions in a variable geometry truss such as found in the airfoil of today's aircraft.